Brake device

ABSTRACT

A peripherally grooved rotary disc, a pair of pivotally connected arcuate shoes relatively swingable into and out of braking engagement within the disc groove, interconnecting means for effecting relative swinging of the shoes, and reinforcing means for enhancing the braking action of the shoes.

United States Patent Mallinger 1 Apr. 25, 1972 54] BRAKE DEVICE1,703,313 2/1929 Loughead ..l88/361 X 1,812,036 6/1931 Christensen..l88/77 X [721 Malling chlds Street 1,875,436 9/1932 Frese ...188/77 xwwdbury, @3095 2,526,935 10/1950 Coker ...l88/77 ux 22 Filed; 7 19703,033,320 5/1962 Edwards.... ..l38/70 3,220,514 11/1965 Erickson..l88/77 [21] Appl. No.: 61,946

Primary Examiner-Duane A. Reger 521 U.S. c1. ..188/77 R, 188/361 Ymme 511111. C1 ..F16d 49/12 [57] ABSTRACT [58] Field of Search l 88/75-77, 70R,

33 70 3 3 A peripherally grooved rotary disc, 21 pair of pivotallyconnected arcuate shoes relatively swingable into and out of brak- 56]References Cited ing engagement within the disc groove, interconnectingmeans for effecting relative swinging of the shoes, and reinforcingUNITED STATES PATENTS means for enhancing the braking action of theshoes,

1,673,211 6/1928 Staude 188/77 16 Claims, 8 Drawing Figures BRAKE DEVICEBACKGROUND OF THE INVENTION As is well known to those versed in the art,there have been experienced certain drawbacks in connection with discbrakes. For example, difficulty has been experienced in b taining largesurface area for frictional engagement without excessive wheel size, itbeing difficult to obtain self-energizing braking action in certain typedisc brakes, and the requirement of a piston and cylinder assembly foreach shoe being problematic in some designs.

SUMMARY OF THE INVENTION Accordingly, it is an important object of thepresent invention to provide a unique disc type brake constructionwherein a large surface area is available for frictional braking actionto minimize wear and wheel size, the braking action being selfenergizingif desired, and wherein relatively large or heavy duty brake devices asfor large vehicles require only a single piston and cylinder assemblyper brake.

It is a further object of the present invention to provide a brakedevice of the type described wherein braking action takes placesubstantially 360 about a disc, and wherein the piston and cylinder maybe located sufficiently removed from the disc and shoes so as to belocated in a cooling atmosphere.

It is still a further object of the present invention to provide a discbrake device having the advantageous characteristics mentioned in thepreceding paragraphs, which is capable of utilizing a pair of arcuateshoes in a single peripheral disc groove, or selectively additionalpairs of shoes in additional disc grooves, and which is extremely simplein construction for economy in manufacture, durability in use, and easeof maintenance and adjustment.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawings,which form a material part of this disclosure.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, which will beexemplified in the construction hereinafter described, and of which thescope will be indicated by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view,partly in section and partly broken away, illustrating a brake deviceconstructed in accordance with the teachings of the present invention.

FIG. 2 is a sectional elevational view taken generally along the line2-2 ofFIG. 1.

FIG. 3 is a partial sectional view taken generally along the line 33 ofFIG. 2.

FIG. 4 is a side elevational view, partly broken away, similar to FIG.1, but illustrating a slightly modified embodiment constructed inaccordance with the teachings of the present invention.

FIG. 5 is a sectional elevational view taken generally along the line 55ofFIG. 4.

FIG. 6 is a partial sectional view taken generally along the line 6-6 ofFIG. 4.

FIG. 7 is a fragmentary sectional view taken generally along the line7-7 ofFIG. 4.

FIG. 8 is a partial elevational view similar to FIG. 4, but enlarged forclarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the braking device of thepresent invention has been illustrated and described herein as appliedto the wheel of a vehicle, it is appreciated that the instant brakingdevice is capable of many varied applications, all of which are intendedto be comprehended, the description and illustration being by way ofexample and without limiting intent.

Referring now more particularly to the drawings, and specifically toFIGS. l-3 thereof, a braking device of the instant invention is theregenerally designated 10, and may include an axially rotatable disc 11adapted to be carried by a vehicle wheel 12 for rotation therewith. Thatis, a wheel hub 13 is mounted, as by bearings 14 and 15 on an axle 16,the inner end of the axle, as at 17, being suitably connected to anappropriate support structure. The disc 11 is circumposed about thewheel hub 13 and suitably fixed thereto, as by bolts 18 or otherfastening means. The wheel 11 is also suitably fixed to the hub 13, inany conventional manner.

The brake disc 11 may be of aluminum or other suitable material,aluminum being chosen for its light weight, strength and heatconductivity. The circumferential or peripheral surface 20 of the disc11 is formed with an annular, circumferential, radially outwardlyopening or facing groove 21. Fixed in the peripheral groove 21, by anysuitable means (not shown), there is provided an insert 22 extendingentirely about the groove, having a constant cross-sectionalconfiguration and conforrnably engaged within the groove. In practice,the annular insert 22 is preferably of sectional construction permittingof assembly with the disc 1 1 in the groove 21.

As best seen in FIG. 2, the insert or disc liner 22 includes a bottomwall 23 extending about the bottom wall of the groove 21, and a pair ofouter side walls extending circumferentially about opposite side edgesof the bottom wall 23 an projecting radially outwardly therefrom, as at24 and 25. It will be seen that the outer side walls 24 and 25 extend ina divergent or radially outwardly flaring relation with respect to eachother, terminating at the peripheral disc surface 20. In addition, thedisc groove liner 22 includes an annular intermediate wall 26 extendingcircumferentially about the annular bottom wall 23, laterally mediallythereof, and projecfing radially outwardly spaced intermediate the sidewalls 24 and 25, being radially coterminus with the side walls 24 and25, and disc periphery 20. In practice, the sectional liner 22 may befabricated of cast iron, or other suitable frictional wear-resistantmaterial.

It will now be appreciated that the disc liner 22 serves to definewithin the peripheral region of the disc 11 a pair of spaced,side-by-side annular grooves 28 and 29, opening radially outwardly fromthe disc throughout their circumferential extent. Further, in thepreferred embodiment, the intermediate wall 26 is generally flat, havingparallel, oppositely facing surfaces 30 and 31 disposed generally normalto the axis of the disc, as defined by the axle 16. The outer side walls24 and 25 have their respective surfaces 32 and 33 facing toward theintermediate wall surfaces 30 and 31, and being convergent toward therespective facing surface in the radially inward direction. Thus, thesurfaces 32 and 33 are disposed in radially inwardly convergent relationwith respective surfaces 30 and 31, and in angular relation with respectto the rotary axis or the axis of axle 16.

In each groove 28 and 29 are disposed a pair of elongate, arcuate brakeshoes, each pair of shoes being connected together for relative swingingmovement toward each other into braking engagement within the respectivegroove and away from each other out of said braking engagement. Moreparticularly, a pair of arcuate, generally semicircular brake shoes 35and 36 are disposed in end-to-end relation extending substantiallycompletely about and within groove 28, while a substantially identicalpair of arcuate, semicircular shoes are arranged in generally circularrelation and disposed conformably within groove 29, as at 37 and 38.Each pair of endto-end arranged brake shoes is pivotally connectedtogether at one adjacent pair of ends, the lower ends as seen in FIGS. 1and 2, as by suitable pivot means 39. The pivot means or pin 39 mayextend through and connect both pairs of shoes 35 and 36, and 37 and 38.Thus, the end-to-end generally semicircular shoes 35 and 36 have theirlower adjacent pair of ends pivotally connected together, as do theend-to-end generally semicircular pair of shoes 37 and 38. The generallyarcuate shoes 35, 36, 37 and 38 each has its radially inner region of asubstantially constant, generally wedge-shaped cross-section,

best seen in FIG. 2, and provided with suitable lining material on itsopposite sides, say of asbestos composition or other suitable material.The wedge-shaped cross-sectional configuration of each shoe 35-38, andits surfacing material or lining,

is conformably received in a respective disc groove 28 and 29 andfrictionally engageable therein upon relative swinging movement of thepivotally connected shoes toward each other.

A brake shoe operating mechanism is generally designated 40, andinterconnected between the upper, nonpivoted ends of the brake shoes35-38. The operating means may include a single cylinder 41 having itsopposite ends open and provided with a pair of pistons 42 and 43 havingpiston rods 44 and 45 projecting oppositely outwardly through respectiveopen cylinder ends. The cylinder 41 may be mounted by any suitable means(not shown) to a fixed structure of the vehicle, and is provided with amounting member 46 extending oppositely beyond the cylinder ends andthere provided with bearing members or ears 47 and 48. A pair of levers49 and 50 are,

respectively, pivotally connected by pins 51 and 52, to ears 47 A and48. More particularly, the lever 49 is pivotally mounted intermediateits ends to the cars 47, while the lever 50 is pivotally mountedintermediate its ends to the ears 48, and the levers 49 and 50 each haveone end located for bearing engagement with a respective piston rod 44and 45. The cylinder 41 is located radially outwardly beyond and offset.from the plane of the disc 11, as best seen in FIG. 2; and, the levers49 and 50 extend at their inner ends 53 and 54 into position directlyradially outwardly of the disc 11 adjacent to the upper ends of shoes35-38. The shoes 35-38 are each provided at its upper end with anupstanding lug, as at 55-58, respectively, Resilient means, such as coilcompression springs 59 and 60 may be interposed between the upperadjacent pairs of brake shoe ends, to urge the relatively swingableshoes apart. For example the coil compression spring 59 may beinterposed between the upper'end lugs 55 and 56 of pivotally connectedshoes 35 and 36, while the coil compression spring 60 may be interposedbetween the upper end lugs 57 and 58 of the pivotally connected shoes 37and 38, A force equalizing engaging member 61 is interposed between theinner end 53 of lever 49 and both of the upper shoe and lugs 55 and 57,while a similar force equalizing engaging member 62 is interposedbetween the inner end 54 of lever 50 and both of the upper end shoe lugs56 and 58. It will thus be appreciated that the application of fluidpressure to the interior of cylinder 41, between pistons 42 and 43,causes the pistons to separate, thereby swinging the levers 49 and 50 tocause their inner ends 53 and 54 to swing toward each other against theresilient forces of springs 59 and 60. The pivotally connected pairs ofshoes 35 and 36, and 37 and 38 are thus swung toward each other and intofrictional braking engagement within their respective grooves 28 and 29.Of course, release of fluid pressure in cylinder 41 releases the brakingaction by the resilient forces of springs 59 and 60. An adjustment ofthe braking action may be conveniently provided at the engagement oflevers 49 and 50 with their respective piston rods 44 and 45, as byadjustment members or screws 63 and 64.

In addition to the above-described braking action, there is provided aself-energizing mechanism or structure, generally designated 66, forenhancing or reinforcing the braking action. Such reinforcing means mayinclude a cam 67 suitably fixed to adjacent support means and having acam surface 68, which may be generally V-shaped as seen in FIG. 1,located adjacent to the lower end pivotal connection means 39 of thebrake shoes 35-38. Further, a cam follower 69, such as a roller, may bemounted on the pivot pin 39 for rolling engagement of the engagement ofthe cam surface 68. The cam surface is suitably configured such thatupon angular displacement of brake shoes 35-38about the axis of axle 16,the cam follower 69, and therefore the brake shoes 35-38, are caused tobe displaced radially inwardly for enhanced or reinforced braking actionin the grooves 28 and 29. This reinforcing or self-energizing brakingaction is effective upon angular displacement of the shoes 35-38 ineither direction about the axis of axle 16, so that self-energizing isachieved upon braking both in forward and reverse movement of a vehicle,or the like.

Upon release of the fluid pressure to operating cylinder 41, thepivotally connected lower ends of shoes 35-38 are resiliently urgedradially outwardly to automatically release the above-describedreinforcing or self-energizing action. Suitable resilient means, such asa spring wire 70 may be employed to release the self-energizing action.For example, the spring wire 70 may have one end anchored in the fixedcam 67, and have its other end in resilient radially outwardly bearingengagement with the pivot pin 39.

The above-described brake device is admirably well suited to mechanicaloperation, in addition to the above-described fluid pressure operation.Thus, as a safety feature, say in the form of a hand brake, there may beprovided a pair of levers 72 and 73, respectively pivoted intermediateits ends, and each having one end connected to an operating member orpull rod, as at 74 and 75. The other end of each lever 72 and 73 may beprovided with a roller, as at 76 and 77 for bearing engagement with theradially outer sides of a pair of pivotally connected brake shoes 35-38,Thus, upon movement of the pull rod 74 and 75 away from each other, therollers 76 and 77 serve to displace the shoes 37 and 38 toward eachother for mechanically operating the braking device 10.

It will now be appreciated that the braking device of FIGS. 1-3 achievesa braking action at the surfaces 30 and 31 similar to that of aconventional disc brake, but of much greater area, extendingsubstantially 360 about the wall 26. In addition, there is the enhancedbraking effect of the wedge action upon movement of the shoes 35-38 intothe grooves 28 and 29, which wedge action also is achieved throughoutsubstantially 360. This wedge action also compounds the braking actionat the surfaces 30 and 31. Further, there is the above-describedself-energizing or reinforcement of the braking action by the mechanism66, including cam 67 and follower 69.

Considering now the additional embodiment of FIGS. 4-8, the brakingdevice there illustrated is generally designated 10a, and includes adisc 11a fixed to a wheel hub 13a, as by suitable fastener means 18a,the hub being joumaled on an axle 16a having its inner end adapted foraffixation to a suitable frame structure, or the like.

The disc 11a is similar to the disc 11, but may be of less thickness,different over the first-described disc in having its peripheral surface20a formed with only a single circumferential groove 21a having asubstantially constant cross-sectional configuration of radiallyinwardly converging sides terminating in a generally cylindrical bottom.

' The single peripheral groove 21a of disc 11a is provided with a liner1 1a conformably covering the sides and bottom of the groove 21a andfabricated of suitable wear-resistant material, such as iron, or thelike. The liner 22a may be of sec tional construction and fixed in thegroove 21a by any suitable fastening means.

In particular, the liner 22a may include a pair of side walls 24a and25a of generally frusto-conical configuration, similar to thefirst-described liner side walls 24 and 25, and a generally cylindricalliner bottom wall 230 similar to the first described liner bottom wall23. The liner side walls 24a and 25a converge radially inwardly of thedisc Ila terminating at their inner edges at opposite sides or ends ofthe liner bottom wall 23a. The radially outer edges of the liner sidewalls 24a and 250 may be substantially flush with the disc periphery orcircumferential surface 20a.

It will thus be appreciated that there is defined within the liner 22aan annular, peripherally extending groove 28a of a constantcross-sectional configuration tapering in the radially inwardlydirection and being open in the radially outward direction.v

A pair of arcuate, generally semicircular brake shoes 35a and 36a arearranged in generally end-to-end relation to extend substantiallycompletely about and being located within the groove 28a. The shoes 35aand 36a may have their lower ends pivotally connected together bysuitable pivot means 39a, such as a pivot pin extending throughoverlapping portions of the lower shoe ends generally parallel to theaxle 16a. As best seen in FIG. 5, the lower end of shoe 35a may bebifurcated to define spaced ears receiving the lower end of shoe 36a inoverlapping relation therewith, the pivot or pin 39a extending throughthe overlapping lower end portions of the shoes.

The shoes 35a and 36a are each of substantially constant cross-sectionthroughout its length, being disposed spacedly and conformably withinthe groove 28a. That is, the shoes 35a and 36a are generallywedge-shaped in cross-section, for conforming reception in the V-shapedgroove 28a within the disc 11a. There may advantageously be provided onthe sides of the wedge-shaped shoes 35a and 36a a covering of frictionalmaterial, such as asbestos composition or other suitable brakingmaterial for engagement with the groove liner 22a.

As noted above, the brake shoes 35a and 36a are each generallysemicircular, having their upper ends proximate to each other in anupper region of the disc 11a. interconnecting the upper ends of thearcuate brake shoes 35a and 36a is an operating mechanism, generallydesignated 40a, which is effective to move the brake shoes toward andaway from each other, as will appear more fully hereinafter.

The operating means 40a may include an open, generally rectangular frameor yoke 460 having one end fixedly secured to the upper end of the shoe35a. As best seen in FIGS. 4 and 6, the right-hand end of open frame oryoke 46a is fixedly secured to the upper end of shoe 35a. Mountedinteriorly of the yoke or frame 46a, at the left-hand end thereof, is acylinder 410 having one end open toward the right-hand end of the yoke.A piston 42a is slidable in the cylinder telescopically in oppositedirections with respect to the cylinder, and is provided on itsrightward end with a pair of spaced ears 43a projecting toward theright-hand end of the yoke.

The upper end of arcuate brake shoe 36a may be provided with anupstanding lug 56a projecting upwardly into the opening within the yoke460 between the piston 42a and right-hand end of the yoke. Morespecifically, the end lug 56a of shoe 36a is interposed between thepiston carried ears 43a and pivotally connected thereto, as by a pin44a. The upstanding lug 56a may be provided with an enlargement 80facing toward the rightward end of the open frame or yoke 46a, and acoil compression spring 590 may be interposed between the rightward endof the yoke and the lug enlargement 80 to resiliently urge the latter,and consequently the piston 42a leftward away from the rightward end ofthe yoke. As the upper ends of shoes 35a and 36a are respectivelyconnected to the rightward end of the yoke 46a and the piston 42a, theresilient means 59a serves to urge the shoes away from each other abouttheir pivoted lower end connection or pin 39a.

It will now be apparent that the application of fluid pressureinteriorly of the cylinder 41a will effect movement of the piston 42aagainst the force of spring 590 to swing the shoes 35a and 36a towardeach other into braking engagement within the groove 28a.

As in the first described embodiment, a self-energizing or reinforcingmeans 66a may include a cam 67a suitably fixed in position and having agenerally V-shaped cam surface 68a facing radially inwardly of the disc1 la toward the pivot means or pin 39a. The pivot pin 39a may carry oneor more rotatable cam followers or rollers 69a in rolling engagementwith the cam surface 68a. The cam surface is configured so that uponangular displacement of the shoes 35a and 36a, and consequently of thepin 39a about the axis of disc 11a, the pin is caused to move radiallyinwardly of the disc to reinforce or enhance the braking action of theshoes in the disc groove 28a. This reinforcement or enhancement is aself-energized braking action.

While any suitable mounting means may be employed to mount the shoes 35aand 36a relative to the vehicle frame, one such mounting means isillustrated as including a generally T- shaped formation 82 on the upperside of cylinder 41a projecting upwardly toward and terminating short ofa rigid support 83 suitably fixed to the frame. Bearing pads 84, such asteflon for freedom of movement, may be interposed between the formation82 and support 83. Resilient, open looped members or springs, as at maybe engaged beneath the cross part of T- shaped formation 82 and aboutthe support 83 to resiliently and yieldably retain the cylinder 41a inposition. Of course, if desired, the self-energizing or reinforcingmeans 66a may be provided with resilient retraction means similar to theresilient member 70 of the first described embodiment, to insure releaseof braking action upon removal of pressure from the cylinder 41a, byreturn of the pivot member 39a radially outward, and return of thecylinder 41a to an intermediate position of its floating mountstructure.

Suitable brake adjustment means may assume any desired structure, aneccentric type adjustment being shown at 63a.

Also, mechanical application of braking action may be achieved in theinstant embodiment, as for an emergency brake, say by the provision oflevers or arms 72a and 730 respectively swingably by pull rods 74a and75a, and carrying eccentrics 76a and 77a for bearing engagement withrespective shoes 35a and 36a to urge the latter toward each other intobraking engagement within the groove 28a.

From the foregoing, it will now be understood that the present inventionprovides a braking device which affords improved braking action,simplicity in structure, reliability in use, economy in manufacture,installation, maintenance and repair, and which otherwise fullyaccomplishes its intended objects.

Although the present invention has been described in some detail by wayof illustration and example for purposes of clarity of understanding, itis understood that certain changes and modifications may be made withinthe spirit of the invention.

What is claimed is:

l. A brake device comprising a rotary disc having a peripherallyextending groove, said groove being configured to taper radiallyinwardly and opening radially outwardly, a pair of arcuate shoesarranged in end-to-end relation extending conformably along and spacedlywithin said groove, pivot means connecting together one pair of ends ofsaid shoes for relative swinging movement of the shoes toward each otherinto braking engagement within the groove and away from each other outof said braking engagement, operating means interconnecting the otherpair of shoe ends for moving the latter toward and away from each other,and reinforcing means comprising cam means operatively associated incamming engagement with said pivot means to move said shoes radiallyinwardly responsive to angular shoe displacement about the disc axis forenhancing the braking action of said shoes.

2. A brake device according to claim 1, said operating means comprisingfluid actuable piston and cylinder means, and resilient means biasingsaid piston and cylinder means toward a position of shoe movement awayfrom each other.

3. A brake device according to claim 2, said piston and cylinder meansbeing offset from said groove and shoes, and comprising a yoke anchoredto one of said shoes extending toward the other of said shoes, acylinder carried by said yoke and having one end opening toward said oneshoe, a piston slidable in said cylinder through said one cylinder end,and connection means connecting said piston to the other of said shoes,whereby reciprocatory sliding movement of said piston effects shoemovement toward and away from each other.

4. A brake device according to claim 2, said piston and cylinder meansbeing offset from said groove and shoes for increased cooling remotefrom the heat of said shoes and disc.

5. A braking device according to claim 1, said shoes being substantiallysemicircular and combining for substantially circular braking engagementin said groove.

6. A brake device according to claim 5, said shoes being generallywedge-shaped in section for conforming braking engagement in saidgroove.

7. A brake device according to claim 1, in combination with resilientmeans urging said pivot means relative to said cam against the directionof angular shoe displacement for release of said braking action.

8. A brake device according to claim 7, said resilient means beingoperatively connected between said pivot means and cam.

9. A brake device comprising a rotary disc having a peripherallyextending groove, said groove being configured to taper radiallyinwardly and opening radially outwardly, a pair of arcuate shoesarranged in end-to-end relation extending conformably along and spacedlywithin said groove, pivot means connecting together one pair of ends ofsaid shoes for relative swinging movement of said shoes toward eachother into braking engagement within said groove and away from eachother out of said braking engagement, operating means interconnectingthe other pair of shoe ends for moving the latter toward and away fromeach other, reinforcing means operatively associated with said shoes tomove the latter radially inwardly responsive to angular shoedisplacement about the disc axis for enhancing the braking action ofsaid shoes, said disc being provided with a second peripherallyextending groove alongside of said first-mentioned groove, said secondgroove tapering radially inwardly and opening radially outwardly, asecond pair of arcuate shoes arranged in end-to-end relation conformablyalong and in spaced relation within said second groove, and second pivotmeans connecting together one pair of ends of said second shoes forrelative swinging movement of said second shoes toward each other intobraking engagement within said second groove and away from each otherout of said braking engagement, said operating means interconnecting theother pair of ends of said second pair of shoes for moving the lattertoward and away from each other, and said reinforcing means beingoperatively associated with said second pair of shoes to move the latterradially inwardly responsive to angular displacement of said secondshoes about the disc axis for enhanced braking action of said secondpair of shoes.

11. A brake device according to claim 9, said reinforcing meanscomprising a specifically configured cam engageable with said pivotmeans to effect said radial displacement.

12. A brake device according to claim 11, in combination with resilientmeans urging said pivot means relative to said cam against the directionof angular shoe displacement for release of said braking action.

13. A brake device according to claim 9, said operating means comprisingfluid actuable piston and cylinder means, and resilient meansbiasingsaid piston and cylinder means toward a position of shoe movement awayfrom each other.

14. A brake device according to claim 13, said piston and cylinder meansbeing ofiset from said grooves and shoes for increased cooling remotefrom the heat of said shoes and disc.

15. A brake device according to claim 9, said shoes being substantiallysemicircular and combining for substantially circular braking engagementin said grooves.

16. A brake device according to claim 15, said shoes being generallywedge-shaped in section for conforming engagement in said grooves.

t l l

1. A brake device comprising a rotary disc having a peripherallyextending groove, said groove being configured to taper radiallyinwardly and opening radially outwardly, a pair of arcuate shoesarranged in end-to-end relation extending conformably along and spacedlywithin said groove, pivot means connecting together one pair of ends ofsaid shoes for relative swinging movement of the shoes toward each otherinto braking engagement within the groove and away from each other outof said braking engagement, operating means interconnecting the otherpair of shoe ends for moving the latter toward and away from each other,and reinforcing means comprising cam means operatively associated incamming engagement with said pivot means to move said shoes radiallyinwardly responsive to angular shoe displacement about the disc axis forenhancing the braking action of said shoes.
 2. A brake device accordingto claim 1, said operating means comprising fluid actuable piston andcylinder means, and resilient means biasing said piston and cylindermeans toward a position of shoe movement away from each other.
 3. Abrake device according to claim 2, said piston and cylinder means beingoffset from said groove and shoes, and comprising a yoke anchored to oneof said shoes extending toward the other of said shoes, a cylindercarried by said yoke and having one end opening toward said one shoe, apiston slidable in said cylinder through said one cylinder end, andconnection means connecting said piston to the other of said shoes,whereby reciprocatory sliding movement of said piston effects shoemovement toward and away from each other.
 4. A brake device according toclaim 2, said piston and cylinder means being offset from said grooveand shoes for increased cooling remote from the heat of said shoes anddisc.
 5. A braking device according to claim 1, said shoes beingsubstantially semicircular and combining for substantially circularbraking engagement in said groove.
 6. A brake device according to claim5, said shoes being generally wedge-shaped in section for conformingbraking engagement in said groove.
 7. A brake device according to claim1, in combination with resilient means urging said pivot means relativeto said cam against the direction of angular shoe displacement forrelease of said braking action.
 8. A brake device according to claim 7,said resilient means being operatively connected between said pivotmeans and cam.
 9. A brake device comprising a rotary disc having aperipherally extending groove, said groove being configured to taperradially inwardly and opening radially outwardly, a pair of arcuateshoes arranged in end-to-end relation extending conformably along andspacedly within said groove, pivot means connecting together one pair ofends of said shoes for relative swinging movement of said shoes towardeach other into braking engagement within said groove and away from eachother out of said braking engagement, operating means interconnectingthe other pair of shoe ends for moving the latter toward and away fromeach other, reinforcing means operatively associated with said shoes tomove the latter radially inwardly responsive to angular shoedisplacement about the disc axis for enhancing the braking action ofsaid shoes, said disc being provided with a second peripherallyextending groove alongside of said first-mentioned groove, said secondgroove tapering radially inwardly and opening radially outwardly, asecond pair of arcuate shoes arranged in end-to-end relation conformablyalong and in spaced relation within said second groove, and second pivotmeans connecting together one pair of ends of said second shoes forrelative swinging movement of said second shoes toward each other intobraking engagement Within said second groove and away from each otherout of said braking engagement, said operating means interconnecting theother pair of ends of said second pair of shoes for moving the lattertoward and away from each other, and said reinforcing means beingoperatively associated with said second pair of shoes to move the latterradially inwardly responsive to angular displacement of said secondshoes about the disc axis for enhanced braking action of said secondpair of shoes.
 11. A brake device according to claim 9, said reinforcingmeans comprising a specifically configured cam engageable with saidpivot means to effect said radial displacement.
 12. A brake deviceaccording to claim 11, in combination with resilient means urging saidpivot means relative to said cam against the direction of angular shoedisplacement for release of said braking action.
 13. A brake deviceaccording to claim 9, said operating means comprising fluid actuablepiston and cylinder means, and resilient means biasing said piston andcylinder means toward a position of shoe movement away from each other.14. A brake device according to claim 13, said piston and cylinder meansbeing offset from said grooves and shoes for increased cooling remotefrom the heat of said shoes and disc.
 15. A brake device according toclaim 9, said shoes being substantially semicircular and combining forsubstantially circular braking engagement in said grooves.
 16. A brakedevice according to claim 15, said shoes being generally wedge-shaped insection for conforming engagement in said grooves.